Commercial vehicles such as trucks having heavy loads include an exhaust brake for deceleration when driving downwardly on a hill or driving at a high speed by manipulating a foot brake as a main brake device. Such an exhaust brake forcibly suppresses discharge of an exhaust gas in the air after being burned in a combustion chamber of an engine, thus enabling the engine is able to act as a compressor to obtain braking force.
When the exhaust gas discharge is suppressed, combustion conditions such as an air fuel ratio or the like are may not be satisfied since the gas burned in the combustion chamber cannot be discharged through an exhaust pipe which communicates with an exhaust manifold, resulting in the engine turning off. In order to prevent the engine from turning off, the exhaust brake has a check valve opening when a back pressure has equal to or higher value than a reference pressure value.
However, in the related art, since the check valve protrudes toward the engine, there is a design limitation on an engine room layout. In addition, since a housing is provided to install the check valve therein, the overall weight of a vehicle increases, eventually degrading fuel efficiency.